Excitation-dependent fluorescence to phosphorescence ratio of p-N,N-dimethylnitroaniline in ethanol

Abstract

The nature of the excitation-dependent luminescence of p-7V,7V-dimethylnitroaniline (DMNA) is examined. The results indicate that the anomalous luminescence behavior of DMNA is due to subtle differences in the molecular environment rather than a characteristic of the isolated molecule. The luminescent properties are ascribed to different H-bonded or rotameric forms, their energy levels being significantly determined by the local solvent polarity.

Dipolar Triplet States ofp-Nitroaniline andN-Alkyl Derivatives with One-, Two-, and Three-Fold Symmetry

“…4,6,8,9,11 Evidence of slight shoulders on the long-wavelength side of the absorption spectra of DMPNA and 1-PNA are apparent and are probably due to an increased separation between these lowest lying excited singlet levels. Despite this, the overall half-widths are less than for PNA itself.…”

“…[1][2][3][4][5][6][7][8][9][10][11] A common feature found is an extremely short S 1 lifetime and very weak, if any, fluorescence. For PNA itself only phosphorescent emission has ever been observed.…”

“…Studies of the excitation-wavelength dependence of the fluorescence to the phosphorescence ratio and the relative polarization of the emissions for N-methyl substituted PNA indicate the presence of two singlet state transitions within the absorption envelope. [7][8][9][10][11] On the basis of electrochromic effects on the absorption of PNA and its high efficiency in second harmonic generation (SHG), it can be concluded that vertical excitation within the first absorption band leads to a highly dipolar excited singlet state. The dipole moment has been estimated to be approximately 15 D. 2,3,12,13 Intersystem crossing is clearly an important radiationless decay channel for the S 1 state of PNA derivatives.…”

Time-dependent density-functional theory investigation of the formation of the charge transfer excited state for a series of aromatic donor–acceptor systems. Part II

“…These PES are similar to the one computed for the 4DMAB-NO 2 , which is phosphorescent in nonpolar solvents and only single fluorescent in polar solvents. 12,13 For 4DMAB-COOH, no experimental fluorescence spectra measured in nonpolar solvents has been reported in the literature. The authors of Ref.…”

The nature of the excited states of p-nitro-N,N-dimethylaniline

“…Rein the CI procedure. The following values were cently, the nature of the excitation-dependent used in the input geometries:~(phenyl ring) = luminescence of I was elamined by Wild and his 1.4 A, <CCC = 120°, rcN(phenyl carbon-amino students [25]. Their results indicate that the nitrogen) = 1.37 A, rNC(amino nitrogen-methyl anomalous luminescence behaviour of I can be carbon) = 1.5 A, r~~(phenyl carbon-nitro nitroexplained not only in terms of k1~dependence gen) = 1.4 A, rNo = 1.25 A, rc~(phenyl on Aexc but may also be due to the subtle difcarbon-acetyl carbon) =1.47 A, r~0 = 1.2 A, ference in the molecular environment and/or r~~(acetyl group) = 1.47 A, rNO(nitroso group) = presence of different ground state conformers.…”